Campbell’s early research had showed that feeding rats an animal protein diet made them develop cancers. Even more significant, it showed that changing their diet back to plant protein halted the development of the tumours. And putting them back on the animal protein diet again made the cancers start to spread again. The cancer literally could be switched on and off.

[Kelly] decided to put [Campbell’s] findings to work in his own practise, conducting what he calls a “field study” among his patients who developed cancer. He has been doing this now for almost a decade, recording the results meticulously.

What emerged is truly extraordinary. All of the patients who adopted the animal protein-free diet and stuck to it strictly found that their cancer stopped growing and spreading. The tumours became dormant, sometimes even reducing in size.

It’s not as clear-cut as it looks though, because many of his patients concurrently underwent conventional cancer treatment … surgery, chemotherapy, radiation. Still, according to Spain, “conventional cancer treatment alone does not have this success rate.”

Notably, those patients who “became complacent as they got better and could not resist going back to having steaks and fry-ups when their specialists gave them the all clear” saw their cancers return.